The invention relates to the field of wireless communications networks, and more particularly to multi-hop routing protocols used in wireless communications networks without infrastructure.
In known manner, a network without infrastructure, also known as an “ad hoc” network, is a network made up of nodes, e.g. sensors, that are connected node to node without any central control.
In a multi-hop routing protocol, a source node that cannot reach a destination node directly, e.g. because of distance or resource constraints, makes use of intermediate nodes for relaying the message. Thus, the source node broadcasts the message via a wireless link, e.g. a radio link. The message is received by at least one node within communication range of the source node, referred to as a neighboring node, which relays the message in turn to at least one of its neighbors, and so on until the final destination is reached. Nodes interact only with their direct neighbors. They do not know the overall topology of the network.
The protocol operates in two stages. In a first stage, routes are calculated. Then, in a second stage, data packets are conveyed over the calculated routes. The routes are periodically recalculated in order to take account of possible changes in the topology of the network.
The “greedy forwarding” routing protocol, as described for example in the document by Ivan Stojmenovic entitled “Position based routing in ad hoc networks”, published in “IEEE Communications Magazine” is an example of a multi-hop routing protocol. In that routing protocol, routes are calculated by incremental construction. A metric calculated by a node on the basis of information provided by neighboring nodes enables the following node to be selected.
More precisely, the greedy forwarding routing protocol uses two types of information packets: HELLO and DATA. The HELLO packets are signaling messages. The DATA packets serve to convey data. Each node of the network knows its own geographical location and the location of the final destination. Each node exchanges its own location information with its direct neighbors by periodically sending HELLO packets. Thus, each node knows the locations of its neighbors. A node having data for transmission makes use of the location data received from its neighbors in order to select the neighboring node that is closest to the final destination and it transmits the data in one or more DATA packets to this selected node.
That protocol provides very good performance in particular in terms of delays, delivery rates, and power consumption.
Nevertheless, it is very sensitive to falsification of the information used for calculating the metric. For example, the HELLO packet transmitted by a malicious node might contain erroneous location information, e.g. close to the final destination. On the basis of such information, the malicious node is thus always selected from among the nodes neighboring a node seeking to determine a following node. Said node then always transmits to the malicious node those DATA packets that it needs to transmit, but the malicious node does not relay the DATA packets to the following node. It thus suffices for a single malicious neighbor to attract all of the traffic from a node in order to obtain total disconnection between a source node and the destination node.
There therefore exists a need for a routing protocol that is simple, that is robust against attempts at disturbing the operation of the network by piracy, and that consumes little energy.